This study focuses on three well-defined, irradiated populations: the first, persons whose thymus glands were irradiated in infancy; the second, women whose breasts were treated with x-rays for acute post-partum mastitis; and the third, persons given x-ray treatments to the head during childhood. Longitudinal studies of reported morbidity and mortality in these populations and their controls have been ongoing for over 20 years. The effects of irradiation earlier in life on subsequent health remain evident. This application proposes continuation of the longitudinal studies, as well as, a clinical screening program by mammography and thermography for the breast-irradiated series. The objectives of the study are to determine the quantitative risk of and the qualitative nature of radiation-induced neoplastic disease and of diseases with autoimmune features. A second objective is to effect by screening the early detection and treatment of breast cancer in a high-risk population. A histological review will be conducted on all breast cancers that have occurred.